Shelf



FIG. 1 is a top, front perspective view of a shelf showing our new design;

FIG. 2 is a right side view thereof;

FIG. 3 is a left side view thereof;

FIG. 4 is a rear view thereof;

FIG. 5 is a front view thereof; and,

FIG. 6 is a top view thereof.

The broken lines depicting the remainder of the shelf show features that form no part of the claimed design. The broken lines showing lettering in FIGS. 1, 4, and 5 form no part of the claimed design. 

CLAIM The ornamental design for a shelf, as shown and described. 